Coronary Circulation and Temp Flashcards
Which usually supplies the posterior part of the heart, the RCA or LCA?
RCA
What is the arterial plexus that connects the epicardial coronary arteries to the subendocardial arterial plexus?
Myocardial cessel network
Which part of the coronary arteries is most susceptible to compression during systole?
The subendocardial arterial plexus
What general division of the coronary arteries are the most frequent site of MIs?
The subendocardial arterial plexus
What is Ohm’s law?
Flow = ΔP/R
Is ΔP between the coronary arteries and the aorta small or large during ventricular diastole?
Large
Is ΔP between the coronary arteries and the aorta small or large during ventricular systole? What causes this?
Small
caused by increase in coronary artery pressur
Is ΔP between the coronary arteries and the aorta small or large during ventricular ejection?
Small, but nonzero
The LV is maximally perfused during which part of the cardiac cycle?
Diastole
When is the ΔP between the aortic pressure and the at a minimum?
At the end of isovolumic contraction
The magnitude of ΔP is small or larger in the right ventricle compared to the left? What is the consequence of this?
Smaller, meaning that the right ventricle is better perfused
Which point on the cardiac cycle graph corresponds to the lowest level of flow?
The upper right, at the end of isovolumic contraction
What is the equation for tension on the walls of the heart?
T = Pressure x Radius
What happens in dilated cardiomyopathy to wall tension?
Increases at every pressure (d/t increased radius)
What is the equation for the resistance, relative to the radius?
R = r^-4
What is Poiseuille’s law?
R=8ℓƞ/πr4
What specific metabolite that increases in the heart due to increased work causes vasodilation?
Adenosine (from turnover of ATP)
What is the adrenergic receptor in the heart? What is the neurotransmitter that this responds to? What is the effect?
Beta 1
Norepi
Increaes HR
What are the two receptors in the coronary arteries that cause vasoconstriction and vasodilation?
Alpha 1 = vasoconstriction
Beta 1 = vasodilation
(***from book)
Core temperature is regulated within what range?
_+1 degree F
How does core temperature change throughout the day?
Rises from waking, until late evening when it falls
The luteal phase of the estrous cycle in denoted by what change in temperature (increase or decrease)?
Increase
What is the way that the body can increase heat production?
Metabolism (shivering is also an acceptable answer)
What are the four mechanisms of heat transfer that the body uses?
- Radiation
- Conduction
- Convection
- Evaporation
What is radiation?
Infrared heat rays moving down a gradient
Which type of colors reflect radiated heat wave (light or dark?)
Light
What is conduction?
Movement of heat through physical touching of the two objects
What is conductivity? What is air’s conductivity relative to water?
The rate at which heat can be transferred
Air is very low relative to water
Vasodilation utilizes which mechanism of heat transfer to rid the body of excess heat?
Conduction
Vasoconstriction utilizes which mechanism of heat transfer to maintain heat?
Conduction
What is convection?
Transfer of heat by using an intermediate (e.g. heating air to heat a cake)
Is the transfer of heat via convection more efficient in air or water?
Water
Is there any mechanism of heat transfer that does not move down its concentration gradient? If so, which one?
None
What is the receptor and neurotransmitter that innervated sweat glands?
sympathetic fibers, utilizing ACh
What is the effect of humidity on the rate of evaporation?
lowers it
What is the heat sensing center of the brain?
Anterior hypothalamic-preoptic area
Do we have more cold or heat receptors on our skin? What about on our anterior hypothalamus?
More cold than heat on skin.
The reverse is true for the hypothalamus
Where are the three cold/heat receptors located in the core of our bodies (not including skin)?
Spinal cord
Abdominal cavity
Great veins
What is the role of ther posterior hypothalmus in temperature control?
Relay station for sensory inputs from periphery and anterior hypothalamus
Integrates response to warm or cool body
What happens to the rate of heat/cold receptor discharge if the stimulus is maintained?
Sensitization
How is vasodilation of the skin effected?
ANS withdrawal
How do infants maintain body temp if they cannot shiver?
Uncoupling of oxidative phosphorylation in brownt fat
Where is the shivering signal generated from?
Posterior hypothalamus
What is the long term strategy to adapt to cold conditions?
Thyroxine secretion
How does thyroxine secretion lead to a long term increase in BMR? (3)
- Increases thyrotropin releasing hormone
- Increases TSH
- Increases Thyroxine
What happens to the set point of shivering with increases in skin temperature?
Decreases
Can angina increase with hot or cold temps?
Cold
How can heat increase HR?
accelerate slope of the pacemaker potential
